The increase in atmospheric pollution generated by exhaust emissions from conventional gasoline and diesel powered internal combustion engines have caused both federal and state governments to enact laws and establish regulations which impose even greater restrictions on the performance of motor vehicles in the areas of exhaust gas emission and fuel economy. For example, the ULEV FTP 75 standards for gasoline engines that are to take effect in the next few years call for double digit reductions in the levels of noxious emissions over the 1990 ULEV FTP standards (up to 90% in the case of hydrocarbons).
During the start of a cold engine, and before the catalyic converter can warm up to be effective, engine emissions are particularly high. After warm-up and during normal running, the catalytic converter reduces emissions, and the internal combustion engine usually operates at a 14.7:1 air to fuel mixture ratio which also yields reduced emissions. However, when the engine temperature is below a certain point, it is more difficult for all of the fuel to be vaporized, and a choke factor is needed to supply extra fuel. Otherwise, not enough fuel will be vaporized, resulting in a mixture leaner than the desired 14.7:1 stoichiometric ratio. Typically, the first twenty seconds of engine startup operates in a cold start "enrichment" mode in which a richer than stoichiometric air/fuel mixture is delivered. As the engine heats up to normal operation, the additional fuel supplied in the air/fuel mixture is gradually decreased until the desired stoichiometric ratio is reached and the engine is running smoothly.
During the cold start enrichment mode, the increased amount of fuel delivered to the combustion chamber causes an increase in hydrocarbon and nitrous oxide emissions due to incomplete burning of the fuel. At the present levels of allowable hydrocarbon emission, the cold start enrichment mode uses an air/fuel ratio of about 10:1 through 14:1, producing emissions that do not exceed today's standards of 7.0, 0.39 and 0.40 grams/mile for CO, HC/NMOG and NOx. These levels of emissions, however, will have to be reduced to 1.7, 0.040 and 0.20 grams/mile respectively to meet the U.S. government's ULEV FTP 75 emissions regulations in the near future. This represents a 90% reduction in HC emissions over present levels.
Heretofore, manufacturers have provided a number of devices to warm the engine faster and to make the choke more sensitive. However, these devices have been too slow or too complicated to effectively meet upcoming ULEV FTP 75 regulations during that short cold start duration period. Furthermore, catalytic converters provide almost no assistance to reducing emission levels during the cold start period. Thus, what is needed is an uncomplicated apparatus for enabling smooth engine operation during cold starts that produces engine emissions that will meet the U.S. government's future ULEV FTP 75 regulations requirements.
Accordingly, it is an object of the present invention to provide a cold start apparatus which can reduce the amount of excess fuel needed during cold start procedures.
It is also an object of the present invention to provide a cold start apparatus which can reduce the exhaust emissions of an internal combustion engine during cold start operation so as to meet the requirements under the upcoming ULEV FTP 75 regulations governing exhaust emissions.
It is a further object of the present invention to reduce the overall fuel consumption of an internal combustion engine.
It is another objective of the present invention to provide a cold start apparatus that includes self cleaning mode which reduces maintenance requirements.
It is still another object of the present invention to accomplish the above-stated objects by utilizing an apparatus which is simple in design and use, and economical to manufacture.
The foregoing objects and advantages of the invention are illustrative of those which can be achieved by the present invention and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other objects and advantages of the invention will be apparent from the description herein or can be learned from practicing the invention, but as embodied herein or as modified in view of any variations which may be apparent to those skilled in the art. Accordingly, the present invention resides in the novel methods, arrangements, combinations and improvements herein shown and described.